The objective of the proposed project is to develop an in vitro model system for the study of aging-related biochemical changes, and to correlate these changes with in vivo changes in humans. Fibroblasts from subjects with juvenile diabetes are the model of choice because the genetic defect in diabetes is believed to be expressed in the accelerated senescence of fibroblasts in vitro. Collagen synthesis was selected as the biochemical marker of aging becuase it is involved in the pathogenesis of both diabetic angiopathy and atherosclerosis which are aging-related diseases. Carefully controlled studies of aging and collagen synthesis of skin fibroblasts from a homogeneous population of young diabetic and age-matched normal control subjects will be performed. Aging of fibroblasts in vitro will be studied by determining cell and population doubling times, plating efficiency and DNA synthesis. Collagen synthesis will be studied by following the incorporation and hydroxylation of proline in collagen isolated from cell and culture medium. The collagen will be further characterized by chromatography and electrophoresis.